Refractory metal oxide/silica supported nickel cluster catalyst

ABSTRACT

A catalyst that is highly active at low operating temperatures and pressures in the oligomerization of lower olefins such as ethylene is produced by contacting (a) a refractory metal oxide/silica support such as alumina/silica wherein the silica content of the support is from about 2 to about 95 weight percent and the metal oxide content of the support is from about 5 to about 98 percent with (b) a tris(cyclopentadienyl)trinickel dicarbonyl. When used to oligomerize ethylene, these catalysts are characterized by a relatively high reaction rate at moderate temperatures and pressures. Their use permits the production of relatively high proportions of desirable trimer, tetramer, pentamer, and higher olefinic products.

CROSS-REFERENCES TO RELATED APPLICATIONS

Reference is made to applicants' following U.S. applications:

U.S. patent application Ser. No. 151,961, filed May 21, 1980, entitled"Process for the Oligomerization of Ethylene".

U.S. patent application Ser. No. 151,950, filed May 21, 1980, entitled"Process for the Oligomerization of Propylene and Higher Olefins".

U.S. patent application Ser. No. 151,953, filed May 21, 1980, entitled"Alkylation of Aromatics with Propylene and Higher Olefins".

U.S. patent application Ser. No. 151,951, filed May 21, 1980, entitled"Metal Modified Refractory Metal Oxide/Silica Supported Nickel ClusterCatalyst".

U.S. patent application Ser. No. 151,952, filed May 21, 1980, entitled"Use of Metal Modified Refractory Metal Oxide/Silica Supported NickelCluster Catalyst to Oligomerize Ethylene".

The disclosures of the foregoing applications are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to a refractory metal oxide/silicasupported nickel cluster catalyst. More particularly, this inventionrelates to a catalyst obtained by contacting a refractory metaloxide/silica support with a nickel cluster which catalyst ischaracterized by a high activity for the oligomerization of ethylene.

DESCRIPTION OF THE PRIOR ART

It is well known in the art to use a variety of catalysts to oligomerizeethylene to higher molecular weight olefins. The term "oligomerize" hasbeen employed, and is employed herein to describe the conversion oflower olefins such as ethylene to olefinic products of higher molecularweight, e.g., to dimer, trimer, tetramer and the like. The reaction rateand product distribution obtained are highly dependent on the exactcatalyst composition and the reaction conditions employed. Two suchgeneral classes of catalysts are the "Ziegler" types consisting ofaluminum trialkyls and the "Ziegler-Natta" types consisting of aluminumalkyl halides and titanium halides. Major disadvantages of aluminumalkyl catalysts are their highly reactive and pyrophoric nature and thefact that they must be used at relatively high temperatures, e.g.,200°-275° C. and pressures, e.g., 2000-4000 psig (13,790 to 27,580 kPa).Although much milder reaction conditions are used when the aluminumalkyls are used in conjunction with titanium halides, the reaction ratesof both of these prior art types of catalysts are not as high asdesired.

Several heterogeneous supported cyclopentadienyl nickel catalysts havebeen employed to oligomerize ethylene to higher molecular weightolefins. One such process described in U.S. Pat. No. 3,459,826 toBarnett et al employs nickelocene, i.e., bis(cyclopentadienyl)nickel,and an inorganic oxide catalyst support. This process, however, requirespretreatment with elemental hydrogen and yields 84% dimer and trimer.Related processes using (π-cyclopentenyl)cyclopentadienyl-nickel aredescribed in U.S. Pat. No. 3,527,838 and U.S. Pat. No. 3,532,765, bothto Barnett et al.

A non-pyrophoric nickel-supported catalyst is described by MasaruIchikawa in an article entitled "Preparation and Catalytic Activities ofSupported Nickel Clusters on a Silica Surface", J. Chem. Soc., Chem.Comm. (1976), pages 26 and 27. This article disclosestris(cyclopentadienyl)trinickel dicarbonyl and other nickel clustercompounds deposited on silica gel or Vycor glass No. 7930 followed byheating at 120° C. as catalysts for olefin hydrogenation and for the"oxo" reaction. Vycor glass No. 7930 is understood to be 95.6 weightpercent silica, 1.0 weight percent alumina, 2.25 weight percent boricacid, the remaining 0.25 weight percent being unidentified contaminants.

SUMMARY OF THE INVENTION

A non-pyrophoric, nickel supported catalyst has now been found that ishighly active at relatively low operating temperatures and pressures inthe oligomerization of lower olefins such as ethylene. This catalyst canbe produced by contacting (a) a refractory metal oxide/silica oxidesupport such as alumina/silica wherein the silica content of the supportis from about 2 to about 95 weight percent and the metal oxide contentof the support is from about 5 to about 98 percent with (b) atris(cyclopentadienyl)trinickel dicarbonyl.

The tris(cyclopentadienyl)trinickel dicarbonyl used herein has thestructure: ##STR1## wherein R, R' and R" can be the same or different C₁to C₂₀ inclusive, hydrocarbon radicals, and n, n' and n" can be the sameor different integers of 0 to 5, inclusive. The R, R' and R" hydrocarbonradicals can be saturated or unsaturated, they can include aliphatic,alicyclic and aromatic radicals such as methyl, ethyl, propyl, butyl,pentyl, cyclopentyl, cyclohexyl, allyl, phenyl and naphthyl radicals.One or more of the cyclopentadienyl moieties in the foregoingtris(cyclopentadienyl)trinickel dicarbonyl can be substituted so as toform an indenyl moiety or a fluorenyl moiety.

Specific examples of nickel clusters which can be used include:

tris(cyclopentadienyl)trinickel dicarbonyl,

tris(methylcyclopentadienyl)trinickel dicarbonyl,

(methylcyclopentadienyl)bis(cyclopentadienyl)trinickel dicarbonyl,

bis(methylcyclopentadienyl)(cyclopentadienyl)trinickel dicarbonyl,

tris(pentamethylcyclopentadienyl)trinickel dicarbonyl,

(pentamethylcyclopentadienyl)bis(cyclopentadienyl)trinickel dicarbonyl,

bis(pentamethylcyclopentadienyl)(cyclopentadienyl)trinickel dicarbonyl,

(methylcyclopentadienyl)bis(pentamethylcyclopentadienyl)trinickeldicarbonyl,

bis(methylcyclopentadienyl)(pentamethylcyclopentadienyl)trinickeldicarbonyl,

tris(ethylcyclopentadienyl)trinickel dicarbonyl,

(ethylcyclopentadienyl)bis(cyclopentadienyl)trinickel dicarbonyl,

bis(ethylcyclopentadienyl)(cyclopentadienyl)trinickel dicarbonyl,

tris(n-propylcyclopentadienyl)trinickel dicarbonyl,

tris(iso-propylcyclopentadienyl)trinickel dicarbonyl,

tris(butylcyclopentadienyl)trinickel dicarbonyl,

tris(pentylcyclopentadienyl)trinickel dicarbonyl,

tris(indenyl)trinickel dicarbonyl,

(indenyl)bis(cyclopentadienyl)trinickel dicarbonyl,

bis(indenyl)(cyclopentadienyl)trinickel dicarbonyl,

(indenyl)bis(methylcyclopentadienyl)trinickel dicarbonyl,

bis(indenyl)(methylcyclopentadienyl)trinickel dicarbonyl,

(indenyl)bis(pentamethylcyclopentadienyl)trinickel dicarbonyl,

bis(indenyl)(pentamethylcyclopentadienyl)trinickel dicarbonyl,

wherein the indenyl moiety has the structure: ##STR2## wherein (R₁) and(R₂) are the same or different C₁ to to C₁₀ hydrocarbon radicals, n isan integer of 0 to 4, and x is an integer of 0 to 3,

tris(fluorenyl)trinickel dicarbonyl,

(fluorenyl)bis(cyclopentadienyl)trinickel dicarbonyl,

bis(fluorenyl)(cyclopentadienyl)trinickel dicarbonyl,

(fluorenyl)bis(methylcyclopentadienyl)trinickel dicarbonyl,

bis(fluorenyl)methylcyclopentadienyl)trinickel dicarbonyl,

(fluorenyl)bis(pentamethylcyclopentadienyl)trinickel dicarbonyl,

bis(fluorenyl)(pentamethylcyclopentadienyl)trinickel dicarbonyl,

wherein the fluorenyl moiety has the structure: ##STR3## wherein (R₃),(R₄) and (R₅) can be the same or different C₁ to C₁₀ hydrocarbonradicals; y and z can be the same or different integers of 0 to 4; and ais 0 or 1. The (R₁), (R₂), (R₃), (R₄) and (R₅) hydrocarbon radicals canbe the same or different, saturated or unsaturated and include thehydrocarbon radicals as described for R, R' and R".

The metal oxide associated with the silica in the support may be definedby the formula M_(x) O_(y) wherein M is alumium, magnesium, zirconium orthorium, x is an integer of from 1 to 2 and y is an integer of from 1 to3. Specific examples of such compounds include Al₂ O₃, MgO, ZrO₂, ThO₂,etc.

When used to oligomerize ethylene the catalysts of the present inventionare characterized by a relatively high reaction rate at moderatetemperatures and pressures. Their use results in the production ofrelatively high proportions of desirable trimer, tetramer, pentamer, andhigher olefinic products. Additionally, the present catalysts do notexhibit pyrophoric behavior and can be used at lower temperatures andpressures than conventional aluminum alkyl catalysts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A suitable support for use in the preparation of a catalyst compositionof this invention is a metal oxide/silica support wherein the silicacontent is from about 2 to about 95 weight percent and the metal oxidecontent is from about 5 to about 98 weight percent. Preferably, thesupport comprises from about 15 to about 92 weight percent silica andabout 10 to about 85 weight percent metal oxide; and most preferablyfrom about 80 to about 92 weight percent silica and from about 10 toabout 20 weight percent metal oxide. The metal oxide/silica supportsinclude synthetic materials as well as acid-treated clays or even thecrystalline alumina silicates known as molecular sieves, so long as thesilica and alumina contents are within the ranges specified. Thus, anyof the commercially available metal oxide/silicas having the propersilica to metal oxide ratios can suitably be used to prepare thecompositions of this invention. The preferred alumina/silicas arecoprecipitated from aqueous or alcoholic solutions of a silicate such assodium silicate or silicic acid and an aluminum salt such as aluminumnitrate, aluminum sulfate or aluminum chloride. For example, an aqueoussolution of silicic acid and aluminum nitrate produces a coprecipitatewhen treated with ammonium hydroxide at a controlled pH of about 8.Differing physical properties of the coprecipitates result by varyingthe pH during precipitation. The precipitates are an intimate comixtureof silicon and aluminum oxides.

Preferably, the support is calcined prior to contact with the nickelcluster as by heating at a temperature of from about 200° C. to about800° C. and, more preferably, from about 450° C. to about 650° C. for aperiod of from about one to about 24 hours, or even longer, butpreferably about four to about 12 hours. The calcining operation can beconducted in air, but is preferably conducted in an inert atmospheresuch as in a stream of argon or nitrogen. Following the calciningoperation, the support is cooled slowly in an inert atmosphere andstored in the absence of air.

The calcined support is then contacted in the absence of air with thenickel cluster, that is, a tris(cyclopentadienyl)trinickel dicarbonyl.The nickel cluster defined by the chemical formula (η⁵ --C₅ H₅)₃ Ni₃(CO)₂, wherein η is the Greek letter eta, used herein, can be preparedby the method of E. O. Fischer et al described in Chem. Ber., 91, 1725(1958). This compound is a solid at room temperature and is notsensitive to air. The structure of the nickel cluster consists of atriangle of nickel atoms with a cyclopentadienyl ligand bonded to eachnickel in a pentahapto fashion and two triply-bridging carbon monoxideligands. This complex has the structure represented above when each ofn, n' and n" has a value of 0.

One method of contacting the support with the nickel cluster is to use asolution of the nickel cluster in a liquid hydrocarbon solvent which isnon-reactive. Examples of such solvents include pentane, hexane,heptane, cyclopentane, cyclohexane, benzene, toluene, and xylene. Theamount of nickel cluster used is not critical and can vary widely aslong as the nickel content of the product obtained from the reaction ofthe nickel cluster with the support is within the range of about 0.001to about five weight percent, preferably within the range of about 0.05to about two weight percent.

The nickel cluster and the support are contacted at a temperature offrom about 20° to about 200° C. for a period of about 10 minutes toabout 12 hours and, more preferably, for about 15 minutes to about onehour at a temperature of from about 20° to about 100° C. The temperatureand time can vary widely depending upon the solubility-temperatureprofile of the solvent and nickel cluster. They can be contacted in anysuitable reaction vessel such as an autoclave.

The nickel cluster has a low solubility in certain aliphatic andalicyclic solvents such as heptane and cyclohexane. This may result in avery slow transfer and/or an incomplete transfer of the nickel clusterfrom solution to the support. Thus, when using such solvents, adifferent method of contacting the nickel cluster and the support ispreferably used. According to this method, instead of adding the nickelcluster as a solution to the reaction chamber, it is charged as a solidwith the support. After purging the reaction chamber with an inert gassuch as argon or nitrogen, the solvent is then added to the reactionchamber.

Following the necessary contact time to effect deposition of the nickelcluster onto the support, the resultant catalyst composition can beseparated from the solvent diluent and stored, preferably in an inertatmosphere, until ready for use. Separation can be accomplished byconventional techniques such as filtration, centrifugation, anddecantation. The catalyst composition can be dried in an inertatmosphere. Alternatively, the catalyst composition can be used tooligomerize an olefin such as ethylene in the solvent diluent in whichit was prepared.

If the catalyst is to be used in the oligomerization of an olefin, it ispreferred to activate it or preactivate it prior to contact with theolefin, unless temperatures exceeding 100° C. were used in the reactionof the nickel cluster with the support in which case the activation orpreactivation is unnecessary. Activation and preactivation of thecatalyst can be accomplished by heating it in an inert atmosphere at atemperature between about 70° and about 200° C., preferably betweenabout 100° to about 170° C., for from about five minutes to about 4hours, or longer, but preferably about 20 minutes to about one hour. Theterm "activation" as used herein refers to an operation performed insitu in the oligomerization reactor prior to the addition of the olefin;and the term "preactivation" refers to an operation performed externalto the oligomerization reactor.

The catalyst compositions of this invention possess several advantagesover prior art oligomerization catalysts. Thus, their use in theoligomerization of ethylene avoids the use of the highly reactive,pyrophoric aluminum alkyls. Nickel oligomerization catalysts ordinarilydo not result in the production of significant amounts of higher olefinsthan dimers. The novel catalyst herein, however, when used tooligomerize ethylene results in the production of significant amounts ofoligomers higher than dimers, that is, oligomers having up to about 20carbon atoms. Moreover, higher reaction rates are attained at lowertemperatures and pressures than with prior art catalysts.

A critical feature of this invention is that the support must containthe silica and metal oxide within the specified ranges. As shown inExample 4 which follows, if tris(cyclopentadienyl)trinickel dicarbonylis deposited on either pure silica or pure alumina, the resultantcomposition will not oligomerize ethylene. Example 5 which followsillustrates that if the amount of silica and the amount of alumina isoutside the ranges specified for this invention, the resultantcomposition will not oligomerize ethylene.

The compositions of this invention are also useful as alkylationcatalysts as shown in our U.S. patent application Ser. No. 151,953,entitled "Alkylation of Aromatics with Propylene and Higher Olefins",filed concurrently herewith, and for the isomerization of alpha-olefinsto internal olefins. When used to isomerize alpha-olefins, it is notnecessary to activate or preactivate the catalyst.

The following examples illustrate the best mode contemplated forcarrying out this invention. In the examples, the amount of nickel inthe catalyst is reported as weight percent elemental nickel based uponthe total catalyst weight. The activities reported were calculated basedupon the weight of elemental nickel supplied by the nickel complex. Allpercentages are by weight unless otherwise indicated.

EXAMPLE 1

An alumina/silica support was prepared by calcining an alumina/silicamixture comprising 87 weight percent silica and 12 weight percentalumina under argon at 550° C. for 24 hours. Subsequently, 1.50 grams ofthe calcined support was transferred under argon to a 300 cc Magnedriveautoclave which had been previously purged with argon. The autoclave wassealed and again purged with argon by three successive argonpressuring-venting cycles. Into a separate clean, dry bottle wasaccurately weighed 0.0560 gram of tris(cyclopentadienyl)trinickeldicarbonyl. The bottle was fitted with a rubber septum and purged withargon for greater than 0.5 hour. Dry, oxygen-free benzene which had beenpurified by distillation under argon from sodium benzophenone ketyl wassyringed into the bottle and the resulting solution comprising a totalvolume of about 98 ml. was syringed under argon into the autoclavecontaining the silica/alumina support. The contents of the autoclavewere stirred at 500 r.p.m. at 22° C. for 0.5 hour to allow adsorption ofthe tris(cyclopentadienyl)trinickel dicarbonyl onto the alumina/silicasupport. Heating was commenced and the contents of the autoclavemaintained at 150° C. for 30 minutes. The weight percent of nickel onthe support was 1.48.

In order to demonstrate the effectiveness of this catalyst in theoligomerization of ethylene, ethylene was added to the autoclave to atotal pressure of 500 psig (3448 kPa), as needed, to always maintain apressure of 450-500 psig (3103 to 3448 kPa). The temperature wasmaintained at 150°±2° C. After 1.0 hour the autoclave was rapidly cooledto 20° C. and the product mixture removed and analyzed by gaschromatographic techniques. The results are reported in Table I. Anactivity of 1576 grams of oligomer per gram of nickel per hour wasfound.

                  TABLE I                                                         ______________________________________                                                      Selectivity                                                     Olefin        (Percent)                                                       ______________________________________                                        C-4           53                                                              C-6           24                                                              C-8           13                                                              C-10          7                                                               C-12          2                                                               C-14          1                                                               C-16-C-20     Trace                                                                         C-4 Composition                                                               (Percent)                                                       1-butene      11.0                                                            trans-2-butene                                                                              53.4                                                            cis-2-butene  35.6                                                            ______________________________________                                    

EXAMPLE 2

A catalyst composition was prepared under the conditions described inExample 1 using 2.24 grams of the same alumina/silica, 0.061 gram oftris(cyclopentadienyl)trinickel dicarbonyl and 112 ml. of benzene. Afterstirring these materials in the autoclave for 0.5 hour at roomtemperature and an additional 0.5 hour at 150° C., the temperature wasadjusted to 125° C.

In order to demonstrate the effectiveness of this catalyst compositionas a catalyst for the oligomerization of ethylene, ethylene was admittedto the autoclave and maintained at a pressure of 450-500 psig (3103 to3448 kPa) for 1.0 hour. The autoclave contents were cooled, removed andexamined by gas chromatographic techniques. The results are reported inTable II. An activity of 2481 grams of oligomer per gram of nickel perhour was observed.

                  TABLE II                                                        ______________________________________                                                           Selectivity                                                Olefin             (Percent)                                                  ______________________________________                                        C-4                35                                                         C-6                48                                                         C-8                15                                                         C-10               2                                                          C-12               1                                                          ≧C-14       Trace                                                                         C-4 Composition                                                               (Percent)                                                  1-butene           22.3                                                       trans-2-butene     43.9                                                       cis-2-butene       33.8                                                       ______________________________________                                    

EXAMPLE 3

A benzene solution containing 0.01 gram oftris(cyclopentadienyl)trinickel dicarbonyl was stirred with 2 grams ofan alumina/silica support comprising 87 weight percent silica and 12weight percent alumina. The support having a surface area of 450 m² /g.had been calcined under purified argon flow at 550° C. for about 18hours. A gradual decrease in the intense yellow-brown color of thesolution due to the presence of tris(cyclopentadienyl)trinickeldicarbonyl was observed. After one hour, the solution became colorlessand the alumina/silica support had changed color from white tobrown-black, indicating complete adsorption of thetris(cyclopentadienyl)trinickel dicarbonyl onto the support. Theresultant supported nickel cluster was transferred under argon to apressure reactor wherein it was thermally activated by heating at 150°C. This catalyst was then used to oligomerize ethylene at a reactiontemperature of 150° C. for one hour and an ethylene pressure of 35atmospheres. After one hour, the reaction mixture was rapidly cooled to5° C. and the gases were vented from the system. The liquid reactionproduct was analyzed and the results are set forth in Table III. The C-6product was analyzed by capillary column gas chromatography and theresults, which indicate the presence of relatively large amounts ofinternal olefins, are set forth in Table IV.

                  TABLE III                                                       ______________________________________                                                        Selectivity                                                   Olefin          (Percent)                                                     ______________________________________                                        1-Butene        3.8                                                           trans-2-Butene  18.3                                                          cis-2-Butene    12.4                                                          (total Butenes) (34.5)                                                        C-6             36.0                                                          C-8             17.0                                                          C-10            8.7                                                           C-12            3.3                                                           C-14            0.5                                                           C-16-C-20       trace                                                                         100.0                                                         ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                                             Selectivity                                              Compound             (Percent)                                                ______________________________________                                        1-Hexene                    6.56                                              3-Ethyl-1-butene                                                                                         16.69                                              cis, trans-3-Hexene                                                           trans-2-Hexene             32.19                                              n-Hexane                   2.53                                               cis-2-Hexene                                                                                             21.91                                              3-Methyl-cis-2-pentene                                                        3-Methyl-trans-2-pentene   17.29                                              Unidentified C-6           2.83                                                                          100.00                                             ______________________________________                                    

The following example illustrates that whentris(cyclopentadienyl)trinickel dicarbonyl is deposited on either puresilica or pure alumina, the resultant composition will not oligomerizeethylene.

EXAMPLE 4

In a series of experiments, designated A through G, benzene solutions oftris(cyclopentadienyl)trinickel dicarbonyl in the amounts set forth inTable V were deposited on the supports indicated in that table in anappropriate reaction vessel under the conditions described in Example 1.In Experiments A-E, the silica support had a surface area of 350 m² /g.;and in Experiments F and G, the alumina support had a surface area of200 m² /g. Ethylene was added to the reaction vessel to a pressure asindicated in the table and the reaction was conducted at thetemperatures and for the length of time indicated in Table V.

                                      TABLE V                                     __________________________________________________________________________               Experiment                                                                    A   B   C   D   E   F     G                                        __________________________________________________________________________    Support    Silica                                                                            Silica                                                                            Silica                                                                            Silica                                                                            Silica                                                                            γ-alumina                                                                     γ-alumina                          Amount, g. 1.04                                                                              0.6 1.15                                                                              1.25                                                                              2.36                                                                              1.25  1.6                                      Temperature, ° C.                                                                 150 100 150 150 150 150   150                                      Pressure, psig.                                                                          500 500 500 500 750 500   500                                      (kPa)      (3448)                                                                            (3448)                                                                            (3448)                                                                            (3448)                                                                            (5171)                                                                            (3448)                                                                              (3448)                                   Run Time, hr.                                                                            2.1 1.0 1.1 2.0 1.4 2.0   1.7                                      (η.sup.5 -C.sub.5 H.sub.5).sub.3 Ni.sub.3 (CO).sub.2,g.                              0.0560                                                                            0.0375                                                                            0.0362                                                                            0.0381                                                                            0.0235                                                                            0.0569                                                                              0.0266                                   ml. benzene                                                                              96  94  84.5                                                                              86  64  107   77                                       Percent Ni on support                                                                    2.11                                                                              2.24                                                                              1.26                                                                              1.22                                                                              0.41                                                                              1.22  0.88                                     __________________________________________________________________________

In each experiment, the activity, g. oligomer/g. Ni×hr., was found to be0.

In the following example, Experiments I and J illustrate the effect ofvarying the amounts of silica and alumina in the support and ExperimentsH and K illustrate the effect of using an amount of silica and an amountof alumina outside the ranges of this invention:

EXAMPLE 5

Four different supports were prepared by isolating a 100-200 meshfraction and calcining under identical conditions, i.e., each supportwas fluidized in a stream of argon at 550° C. for 5 hours. Thesecalcined supports were used in experiments conducted in an identicalmanner by charging 2.0 grams of the support and 0.01 gram of solidtris(cyclopentadienyl)trinickel dicarbonyl under argon to a 300 cc.autoclave. Purging was accomplished with 3 successive pressure-ventcycles using argon. Cyclohexane (50 ml.) was weighed and syringed intothe autoclave under argon. The contents were stirred at ambienttemperature for 2.0 hours and were then rapidly heated to 150° C. andmaintained at that temperature for 30 minutes. Ethylene was then addedto a total pressure of 500 psig (3448 kPa) and maintained at thistemperature for 1.0 hour. The autoclave was then rapidly cooled to 5° C.and the liquid contents were collected in a tared, cooled bottle andanalyzed immediately by gas chromatography. The results of theseexperiments are shown in Table VI. In this table, experiment H used asupport comprising 85 weight percent silica and 15 weight percentalumina; experiment I used a support comprising 98 weight percent silicaand 2 weight percent alumina; experiment J utilized a support comprising15 weight percent silica and 85 weight percent alumina; and experiment Kutilized a support comprising 2 weight percent silica and 98 weightpercent alumina. In each experiment, the weight percent of nickel on thesupport was 0.21.

                  TABLE VI                                                        ______________________________________                                        Experiment   H        I       J      K                                        ______________________________________                                        Support                                                                       Si, weight percent                                                                         85       98      15     2                                        Al, weight percent                                                                         15       2       85     98                                       Activity,                                                                     g oligomer/g Ni × hr                                                                 5156     0       1734   5                                        Selectivity,                                                                  percent:                                                                      C-4          46               61     100                                      C-6          38               27                                              C-8          13               11                                              C-10         2                1                                               C-12         0.5              0.1                                             Compositions of                                                               C-4, percent:                                                                 1-butene     27               27     33                                       trans-2-butene                                                                             42               41     32                                       cis-2-butene 31               32     35                                       ______________________________________                                    

As seen from Table VI, the dominant effect of the SiO₂ :Al₂ O₃ ratio wasto decrease activity at the two extremes, i.e., 2:98 (Experiment K) and98:2 (Experiment I) yielding activities of 5 and 0 respectively.

EXAMPLES 6-10

A 500 ml. 3-neck round bottom flask was fitted with a magnetic stirringbar, a gas inlet, a stopper and a rubber septum. The flask was purgedwith argon and an alumina/silica support (2.1 grams) comprising 87weight percent silica and 12 weight percent alumina which had beencalcined at about 550° C. under argon was placed in the flask. The flaskwas then purged with a constant flow of argon. Into a separate bottlewas weighed 0.0607 gram of tris(cyclopentadienyl)trinickel dicarbonyl.The bottle was fitted with a magnetic stirring bar, sealed with a rubberseptum and then purged with a constant argon flow. Benzene (70 ml.)which had been purified by distillation under argon from sodiumbenzophenone ketyl (70 ml.) was syringed into the bottle and stirred todissolve the nickel complex. The resulting dark yellow-brown solutionwas syringed into the flask containing the alumina/silica under aconstant flow of argon and the resulting suspension was stirred to allowadsorption of the nickel complex onto the alumina/silica support. After2 hours at room temperature (22° C.), the suspension was filtered underargon to yield a clear orange-brown solution which was a different colorfrom the original solution of tris(cyclopentadienyl)trinickeldicarbonyl. The supported catalyst was recovered as an orange-brownsolid. The weight percent of nickel on the support was 0.27. Using theprocedure described in Example 1, additional catalyst compositions wereprepared using the support, the amount oftris(cyclopentadienyl)trinickel dicarbonyl, and the amount of benzeneshown in Table VII. The weight percent of Ni on the support in theresultant composition is also set forth. In Examples 6 to 9, the supporthad a surface area of 425-450 m² /g; and in Example 10, the support hada surface area of 487 m² /g.

                  TABLE VII                                                       ______________________________________                                                      Examples                                                                      6     7      8      9    10                                     ______________________________________                                        Support:                                                                      Silica, weight                                                                percent         87      87     87   87   75                                   Alumina, weight                                                               percent         12      12     12   12   25                                   amount, g.      2.10    1.30   2.24 0.32 2.08                                 (n.sup.5 -C.sub.5 H.sub.3).sub.3 Ni.sub.3 (CO).sub.2,g.                                       .0607   .0328  .0610                                                                              .0339                                                                              .0228                                Percent Ni on                                                                 Support         0.27    1.01   1.09 3.95 0.45                                 ml. of benzene  70      74     112  83   58                                   ______________________________________                                    

EXAMPLES 11-14

Using the procedure described in Example 5, additional catalystcompositions were prepared using the support, the amount oftris(cyclopentadienyl)trinickel dicarbonyl and the amount of heptane orcyclohexane shown in Table VIII. The weight percent of Ni on the supportin the resultant composition is also set forth. In Examples 11 and 12,heptane was substituted for the cyclohexane of Example 5. In eachexample, the support had a surface area of 425-450 m² /g.

                  TABLE VIII                                                      ______________________________________                                                      Example                                                                       11    12      13      14                                        ______________________________________                                        Support:                                                                      Silica, weight                                                                percent         87      87      87    87                                      Alumina, weight                                                               percent         12      12      12    12                                      amount, g.      2.06    2.00    2.00  2.05                                    (η.sup.5 -C.sub.5 H.sub.3).sub.3 Ni.sub.3 (CO).sub.2,g.                                   0.100   .0102   .0100 .0108                                   Percent Ni on                                                                 Support         0.2     0.21    0.21  0.21                                    ml. of heptane  40      50      --    --                                      ml. of cyclohexane                                                                            --      --      50    50                                      ______________________________________                                    

The following example illustrates the use of the catalyst of thisinvention to isomerize 1-hexene.

EXAMPLE 15

Into a clean, dry sample bottle were placedtris(cyclopentadienyl)trinickel dicarbonyl (0.0076 gram) and asilica-alumina support (0.9347 gram) comprising 87 weight percent silicaand 12 weight percent alumina which had been previously calcined at 550°C. under argon. The support had a surface area of 425-450 m² /g. Thesupported catalyst thus obtained comprised 0.33 weight percent nickel.Dry 1-hexene (16.82 grams) having a purity of 99.8% by gaschromatography, previously purified by distillation from calcium hydrideunder argon, was syringed into the bottle against a countercurrent ofargon and the contents were stirred overnight (about 19 hours) at 21° C.and 0 psig. A gas chromatography sample of the liquid was then taken andanalyzed as follows:

    ______________________________________                                        Olefin         Relative Weight %                                              C-6            89                                                             C-12           11                                                             Compositions of C-6                                                                          Relative Weight %                                              1-Hexene       2                                                              trans-2-Hexene 71                                                             cis-2-Hexene   27                                                             ______________________________________                                    

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof,variations and modifications can be effected within the spirit and scopeof the invention as described hereinbefore, and as defined in theappended claims.

We claim:
 1. A catalyst composition obtained by contacting (a) arefractory metal oxide/silica support wherein the silica content of saidsupport is from about 2 to about 95 weight percent and the metal oxidecontent of said support is from about 5 to about 98 weight percent with(b) a tris(cyclopentadienyl)trinickel dicarbonyl.
 2. A catalystcomposition as defined in claim 1 wherein saidtris(cyclopentadienyl)trinickel dicarbonyl has the structure: ##STR4##wherein R, R' and R" are the same or different C₁ to C₂₀ hydrocarbonradicals and n, n' and n" can be the same or different integers of 0 to5, inclusive.
 3. A catalyst composition as defined in claim 2 whereinthe metal oxide component of said support has the formula M_(x) O_(y),wherein M is aluminum, magnesium, zirconium or thorium, x is an integerof from 1 to 2 and y is an integer of from 1 to
 3. 4. A catalystcomposition as defined in claim 3 wherein the metal oxide is alumina. 5.A catalyst composition as defined in claim 1 wherein the silica contentis from about 15 to about 92 weight percent and the metal oxide contentis from about 10 to about 85 weight percent.
 6. A catalyst compositionas defined in claim 1 wherein the silica content is from about 80 toabout 92 weight percent and the metal oxide content is from about 10 toabout 20 weight percent.
 7. A catalyst composition as defined in claim 4wherein the silica content is from about 15 to about 92 weight percentand the alumina content is from about 10 to about 85 weight percent. 8.A catalyst composition as defined in claim 4 wherein the silica contentis from about 80 to about 92 weight percent and the alumina content isfrom about 10 to about 20 weight percent.
 9. A catalyst composition asdefined in claim 4 wherein the silica content is about 87 weight percentand the alumina content is about 12 weight percent.
 10. A catalystcomposition as defined in claim 4 wherein the silica content is about 75weight percent and the alumina content is about 25 weight percent.
 11. Acatalyst composition as defined in claim 1 wherein saidtris(cyclopentadienyl)trinickel dicarbonyl is defined by the chemicalformula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 12. A catalyst composition as defined inclaim 2 wherein said tris(cyclopentadienyl)trinickel dicarbonyl isdefined by the chemical formula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 13. A catalystcomposition as defined in claim 3 wherein saidtris(cyclopentadienyl)trinickel dicarbonyl is defined by the chemicalformula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 14. A catalyst composition as defined inclaim 4 wherein said tris(cyclopentadienyl)trinickel dicarbonyl isdefined by the chemical formula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 15. A catalystcomposition as defined in claim 5 wherein saidtris(cyclopentadienyl)trinickel dicarbonyl is defined by the chemicalformula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 16. A catalyst composition as defined inclaim 6 wherein said tris(cyclopentadienyl)trinickel dicarbonyl isdefined by the chemical formula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 17. A catalystcomposition as defined in claim 7 wherein saidtris(cyclopentadienyl)trinickel dicarbonyl is defined by the chemicalformula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 18. A catalyst composition as defined inclaim 8 wherein said tris(cyclopentadienyl)trinickel dicarbonyl isdefined by the chemical formula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 19. A catalystcomposition as defined in claim 9 wherein saidtris(cyclopentadienyl)trinickel dicarbonyl is defined by the chemicalformula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 20. A catalyst composition as defined inclaim 10 wherein said tris(cyclopentadienyl)trinickel dicarbonyl isdefined by the chemical formula (η⁵ -C₅ H₅)₃ Ni₃ (CO)₂.
 21. A catalystcomposition as defined in claim 1 wherein said support is calcined,prior to said contact at a temperature from about 200° to about 800° C.for about one to about 24 hours.
 22. A catalyst composition as definedin claim 1 wherein said contact is conducted in the absence of air at atemperature of about 20° to about 200° C.
 23. A catalyst composition asdefined in claim 1 wherein a solution of saidtris(cyclopentadienyl)trinickel dicarbonyl is contacted with saidsupport.
 24. A catalyst composition as defined in claim 23 wherein saidsolution is a benzene solution.
 25. A catalyst composition as defined inclaim 23 wherein said solution is a cyclohexane solution.
 26. A catalystcomposition as defined in claim 1 wherein the nickel content is fromabout 0.001 to about five weight percent.
 27. A catalyst composition asdefined in claim 1 wherein the nickel content is from about 0.05 toabout two weight percent.
 28. A catalyst composition as defined in claim14 wherein the nickel content is from about 0.001 to about five weightpercent.
 29. A catalyst composition as defined in claim 14 wherein thenickel content is from about 0.05 to about two weight percent.
 30. Acatalyst composition as defined in claim 1 wherein said contact iseffected at a temperature from about 20° to about 200° C. for about 10minutes to about 12 hours.
 31. A catalyst composition as defined inclaim 1 wherein said contact is effected at a temperature from about 20°to about 100° C. for about 15 minutes to about one hour.
 32. A catalystcomposition as defined in claim 14 wherein said contact is effected at atemperature from about 20° to about 200° C. for about 10 minutes toabout 12 hours.
 33. A catalyst composition as defined in claim 14wherein said contact is effected at a temperature from about 20° toabout 100° C. for about 15 minutes to about one hour.
 34. A catalystcomposition as defined in claim 1 wherein the solidtris(cyclopentadienyl)trinickel dicarbonyl is contacted with saidsupport and a hydrocarbon solvent is then added.
 35. A catalystcomposition as defined in claim 34 wherein said hydrocarbon solvent isbenzene.
 36. A catalyst composition as defined in claim 34 wherein saidhydrocarbon solvent is cyclohexane.
 37. A catalyst composition asdefined in claim 1 which is thereafter activated or preactivated byheating at a temperature of about 70° to about 200° C. for about fiveminutes to about four hours.
 38. A catalyst composition as defined inclaim 1 which is thereafter activated or preactivated by heating at atemperature of about 100° to about 170° C. for about twenty minutes toabout one hour.
 39. A catalyst composition as defined in claim 14 whichis thereafter activated or preactivated by heating at a temperature ofabout 70° to about 200° C. for about five minutes to about four hours.40. A catalyst composition as defined in claim 14 which is thereafteractivated or preactivated by heating at a temperature of about 100° toabout 170° C. for about twenty minutes to about one hour.